Add require: false to Gemfile example

[r7kamura]

If you run require 'rspec/core' before the appropriate timing, Kernel.#context would be defined unexpectedly and you will get a warning when you load irb. The following Issue provides more information on this issue.

• irb: warn: can't alias context from irb_context. (3.5.0.beta4 and 3.5.0 final) rspec/rspec-rails#1645

This Gem executes require 'rspec/core' when loaded, so if it is loaded in a Rails app with Bundler.require it will cause this problem. This pull request solves this problem.

rspec-retry/lib/rspec/retry.rb

Line 1 in 06a9595

require 'rspec/core'

$ bin/rails c -e test
Loading test environment (Rails 7.0.4)
irb: warn: can't alias context from irb_context.
irb(main):001:0> exit

Since the README already explains to write require 'rspec/retry', there is no problem to explain to add require: false like this.